Sahih Bukhari Volume 2, Book 26, Hadith Number 641.

Narated By Jabir bin ‘Abdullah  : We came with Allah’s Apostle (to Mecca) and we were saying: ‘Labbaika Allahumma Labbaik’ for Hajj. Allah’s Apostle ordered us to perform ‘Umra with that Ihram (instead of Hajj).